Quick drying printing ink and method of preparation



Patented Aug. 19,1941

QUICK DRYING PItlNTlNGplNK AND METHOD OF PREPARATION Joseph G. Curado, Rutherford, N. J., assignor to General Printing Ink Corporation, New York, 1 N. Y., a corporation of Delaware No lirawing. Application March21, L ScrialNo.197,308 2 2 Thisinvention relatestofimproved, quick dryjing printing inks andparticularly' to'a method of fore, remains entirely uponthe surfaceand conpreparing printinginks suitablefor printing on metals orother substantially non-absorbent materials which permit practicallynopenetration of the ink. 2 2 2 An object of the inventionis toproduce an ink for printing on metals such as tin or tin plate for on similar] nonabsorbent surfaces, which will dry in a much shorter time on baking than do the commonlyused tin printing inks.

Afurther objectis to produce an ink for print.- ing on metallic or similar surfaces, which ink not only" dries in a very shortjtime, butalso re sults in a very flexible, adherenhhardand relatively scratch-{proof mm on baking.

A still further object islto produce an ink for printing on metals which will be; so hard and resistant to abrasion, that no top coating of varnish or similar, material will be required to protect theink film from sjcr'atchingfor marring during the fabrication and'use of the printed 2 article. a 2 2 2 These objects are accomplished by, combining 2 2 certain heat reactive oils and reslns in 2a two- 2 stage varnishing making process in such away oven either continuously or in batches. The

sequently cannot be touched without smudging until it has practically completely dried. This drying is customarily accomplished by stacking the inked sheets in racks and baking in a: heated baked sheets are then varnished to impart gloss and protection to the ink, and again baked to setthe varnish. The decorated sheets are then "cut and formed into the desired shapes, such as cans,lboxes, etc., with suitable cutting and formingtools a A 2 Inks whicha're to he used for metal decorating should be resistant, to darkening or color change during the baking operation; they should have good adhesion to the metal sur facefand should remain flexible after bakingto permitthe drastic deformations incidenttothe shapingqand fabricating operations. Theyshould dry as quickly as possibleunder the conditions of the ovens, and

g should not react with the subsequent, varnish thatLthe majorportion of the polymerization or I "drying? takesyplace during the cooking rather than after application of theink to the printing surface.

Prior art,

The art of decorating metals,p=particularly tin and tin plate, is practiced widely as a step in the production of cans, boxes, containers, clo- 1 sures, display] signs arid other products; var 2 ions decorative designs or lettering are often printed on metal sheetsusing transparent coat- 1 lngs or colored inks as the decorativemedium.

Metal printing is usually done by the offset printing process; and as ordinarily used, generally employs threecylinders in contact with 2 one another.

the name implies, carries the printing plate and runs in contact withthe inking mechanism. The center or blanket-cylinder runs in contact with the plate cylinder and carries a rubber blanket which receives .ink from the platecylinder, and ,oflsets it tothesheet: The third, or impression cylinder, holds the, sheet of metalagainst the blanket cylinder while the impression is being 2 transferred. 2 z 2 As the metal sheets are impervious to the ink,

the latter cannot dry by penetration or absorptioninto the printed medium. The ink, there- The upper, or plate cylinder, as

coating. 2 2, 2 a

The balancing of an ink composition to the conditionsof the ovens requires considerable skill and knowledgeof materials and their reactions upon heating to varioustemperatures and for various lengths of time.

According to Wolfe (Manufacture of Printing and Lithographic Inks, ;N. Y. McNair Dorland C0,, 1933), p. 202-204, tin printing inks havef usually consisted of pigments ground lnalithographic or transparent varnish (linseed oil) togther with a small amount of drier. In general, b king times rangefrom 15 to 25 minutes attem- 2 2 peratures between200 ,and 280 F.

' Ajs modern production methods tend to increasing speeds, the necessity of baking for the relatively longtime of 15 m 25 minutes slows 2 down ,the au xilia'ry processesto the capacity of the,2ovens in the case offlthe batch process, or necessitates a tremendous amount of tunnel drying equipment, occupying a large floor space area 'in the case or. a continuous, conveyor drying process, where the speedof the conveyor through 'the tunnel ishigh. Naturally, the shorter the drying tunnel, theslower; the speed with which it must be traversed by the printedsheetjto provide any desiredpredeterminedbakingtime, If

the oven is longer, the conveyor can, of course,

be speeded up. a proportional amount for a given baking time. 2,

The,tendency and urge toward higher speeds, 2

existing in all commercial operations, is faced here withseveral theoretical alternatives. Either a higher temperature could be maintained; a

longer drying tunnel could be provided for the same baking conditions, thus allowing increased speed of the conveyor; or a faster drying ink couldbe used. I v

Excessively high temperatures, however, are

not only costly to maintain, but have'been found to bevery'detrimental to the coatings, which discolor andbecome embrittled on exposure to high temperatures, wherebythe beauty of the 1.

printed effects isimpaired, and the flexibility so necessary in subsequent forming operations, is destroyed.

f Many plants have installed longer drying tunnels, but these are not only very costly to install and operate, but require a great deal of floor space, more than is often available in existing v entails a com+ plete redesigning of the planter the building. of

plants, so that their use sometimes a new'one. I V

lhe desirability of mink which would my faster under existing or simplified conditions has long been'recognizedpbut several factors have militated against its development.

V Film forming materials dissolved in volatile solventsare unsatisfactory for this type of print- ,ing, as they dry too rapidly and set on the inking rolls before they reach the work; Moreover,

- cellulose derivatives, which usually form the basis of such lacquers, have notoriously poor'jadhesion 1 to metals such as tin and tin plate, unless supplemented by' resinsin suchproportions as to pro-'- v duce a brittle fllni, Such 'coatings'al'so lack the flexibility necessary for the die forming opera- .tions to which the decorated metal must be sub-- I Jected. Simple "spirit varnishes," that is," solutions of resins in solvents, usually alcohol,-while I generally excellent in adherence, are objection-hm able for the same reasons as the lacquers; in drying too rapidlyon-the printingrrolls, and-inprc ducing brittle films which' -will-notstand 'fabri cat1011- As pointed out above, the: presently'used oil inks meet as many ofthe'conditions torsatis factory'metal printing inks as any so far devel' 1 oped. Such inks, however, are veryfslow drying,

even'at the elevated temperatures of 'the baking ovens, and result in films which are so soft and subject to marring and abrasion that a'protecto prevent scratching or marring die for mation of the product and in subsequent use:

plication-to thework, the troublesome tender" or soft stage-can be passed in the kettle, and.

the resulting ink be made to dryin a relatively much shorter time at the same temperature in the oven.

Such a procedure has previously been thought impossible, as hardening or gelling took place in the ink cans'whenever polymerization had been made to proceed too far in the varnish kettle.

My results, are accomplished by cooking my varnish to the point of incipient gelation, then adding additional materials including solvents, and further cooking to the desired tackor body. in carrying out my invention I select my varnish ingredients from among the drying and semi-drying or non-drying oils commonly used in ink making, and combine these oils with resins as'in varnish making practice. However, I prefer to select, my resins from the class of oil soluble synthetic resin materials suchias those of the-heat reactive type. Examplesof these are the heat reactive phenol resins which have been modified with other materials such as alkyl derivatives, natural resins, oils, oil acids and the like, although other heat reactive resins may i also work satisfactorily. One of the'most satisfactory resins for my purpose is one of the type of alkyl substituted phenol-formaldehyde condensation product modified with-Chinese wood oil. (tung pin and particularly the phenyl substituted product. In referring to resins modifiedywith various constituents,..I use the term have beencomlwunded modiiiedfin the sense commonly used in resin manuiactureto mean that all the ingredients,

including the modifier. are combined during resinification, so that a homogeneous compound or mixture results. (See The Chemistry of Syndi thetic' Resins," by Carleton Ellis, Reinhold Pub.

1.935, chapters 19 and 20, entitled Modifled -"Phenolaldehyde Resins.)

gredients, together with-solvents and plasticizers according-to my improved method, the finished varnish can be used alone or with additional oil and other ingredients as "a grinding medium for the various pigments,

lakes and toners commonly used in metal dec- ..oratinginks.v --1.

tive coating of varnish or thelike must be'appliedj Moreover, the drying reaction, (readily acombi- 1 nation of oxidation and polymerizationhas' it e I takes place in the oven is not a simple one'in which the film becomes progressively harder as the heating proceeds. There appears to be an initial skinning over of the film, and then, Just before the film becomes hard enough to-handle or touch, it passes'through a soft or "tender stage, during which it can be easily marked or marred. The reason for. thisbeh'avior is not completely understood, but it is a stage quite universally observed in the polymerization of oil and certain other polymerizable materials.

Accordingly, if the metal sheet is removed from the baking oven a few moments too soon, the coating is liable to be in the soft stage and very ent a critical minimum of drying time for a given drying temperature below which it has been impossible to go.

;I have now discovered that by properly selecting my varnish ingredients, and by carrying out a major proportion of the polymerization of the varnish during its preparation, 1. e., beiorc ap- I sensitive to marring. Thus'there is always pres- In making up thisvarnish, the resin and An example of my varnish base is given below inparts byweightn v v Phenyl substituted phenohformaldehyde resin modified with tung oil (Bakelite No. 302 resin) 1140 Raw tung 011 490 Blown castoroil; "60 Benzyl alcohol 2'75 Dimathyl phthalate 390- tung oil were heated to C. in hour. The heat was then shut off but the temperature continued to rise. When the mass had attained a tem-- perature of 200 0., gentle heat was again applied for about hour, and then the temperature was raised quickly to 240 .Cwan'd held at this temperature until the mass had" attained its maximum body short of gelation. The remaining ingredients were then added, and the temperature was raised to 210 C. and held at this point under refluxing conditions until the varnish had reached the desired consistency or body, which in this case was about 3 hours.

Afterthese insemi-drying o'r non-drying oils in varnish making.

After, application tometal and baking at.

200-220 F. for three minutes,this varnish was hard and tack free, and after 24 hours had aged sufilciently to permit die forming and fabrication of the decorated metal. c Other modified phenol resins besides-the one givenin the example can be used, provided they are of the heat reactivetype, which tend to.

"body" or form a: gel on heating. These resins have the general characteristics of the resins described in U. 3. Patent 2,073,229. to Shuey,.

althonghthe patent refers more specifically to alkyl substituted phenol-'formaldehyde resinsprepared in combination with linseed o1l, whereas drying oils which tend to gel on heating may be used, such as tung oil (Chinesewood on),

oiticica oil, perilla oil. certain of the modified caster oils such as thatfknownin the trade as Isolene, and also linseed oil, although the latter requires a somewhat longer time -to set than do the other oils ,mentioned, and moreover produces softer films than inks made withother place of castor oil.' I may useany of-the commonly used abilityto dissolve the gels formed in the polymerization of the resin-oil complexes, as well as of the cools-is indicated when a cooled pill of the varnish refuses to elongateto a thread or string more than3 inches in length, and breaks off in a rubbery manner;

Solvents and plasticizers are added at this point, and the mass isheated'to about190-200 0., under refluxing conditions until the desired body. has beenreached, generally after about 2% to 3 hours. Immediately after addition of the solvent, the varnish presents a rather gelatinous and stringy appearance. After about 1%to 2 hours of cooking, most of the lumps have disappeared, and the varnish begins to be shorter and i less tacky. After about a. half hour'more, the i varnish compares -in tack with standard varnishes oi this type, and is ready for application as a clear ink, or for in- J corporation, of pigments in the usual "way; with 1 sary to adapt it to the diiferent properties of the .F or without the addition of additional oils, waxes,

etc. The point at which the solvents are added is a critical one, as the-addition must be made at the moment whenthe varnish has reached its maximum body but-before the gels have. set.

Anydesired color can be compounded from this type of base. .with the modifications necesdifierent pigments and colors: Such modifications are customaryand are-well recognized in for their low solvent action on the rubber prints ing rolls and blankets. The glycol derivatives,

while they produce satisfactory inks, are undesirable because they have a somewhat deleterious efiect on rubber. Aside from their action on the rubber rolls and blankets of the printing press,

such solvents as the glycol derivatives mentioned l i above, i. e., ethers of .monoor .di-ethylene gly- Iool, tetralin, ,hexalin, cyclohexanone and the like would be satisfactory. and c'an be usedwhere roll replacement 'is not an important factor; Benzyialcohol', on the other hand; has noapprei ciable solvent action on the rubber rollaand is i aniexcellent solvent for the-complex gels'formed in the cooking. It is therefore specified as the preferred solvent. Plasticizers such as dimethyl phthalate and diamyl phthalate',- (which are also I solvents) are preferred as they have very little harmful effect on the. printing rolls. Dibutyl phthalate tends to swell rubber very slightly. but isotherwise a satisfactory plasticizer, as are also triphenyl phosphate, tricresyl phosphate, castor oil, triacetin and the like.

The cooking conditions will vary somewhat." f

depending on the heat reactive ingredients used in the first stage. Inthis stage the reaction is exothermic, giving 011 heat as'it proceeds. The

rise in temperature to the desired maximum, 1. e., to the point of incipient gelation, should .be steady. Therefore, the heat should be shut off at a predetermined point before the maximumis a weight. a

Q JixurrtrIL-Blaelc ink Varnish-of Example I. 60 Blown tung o'il 14 Milori blue "..;.L 4 Lamp black- 24 Drier v I "Carnauba wax (50% solution in benzyl alcon -J--=, 3 a

i e W Exam ne TIL-Green ink Varnish of Example I... 2i Blown tung 10 *flchrome yellow, lem0n 11.5

Chrome yellow, medium 16 .Milorl'jblue I l 12.5 Alumina hydrate 6 Titanium dioxide ;Ls 28 I: a 108- EXAH PL! Iv.-Blu8tnk Varnish of Example 'I.. 58" Blown tung oil 24 Tungstate purple toner 48 Milori blue I i v i 9.5 Ultramarine blue 1'7 Lithol red (dry 1 i q 1 i i 1 157.5 1 Exmru V.-Red ink P Varnish of Example I 26 Blown .tung oil 10.5 Litholrubine'toner 6.2

Cadmium red 36.09 "Cadmium yellow 12.53 Alumina hydrate e -1 8.73 i 3.44

the ink making industry.

Examples of diiferent colored inks according .7 --to.my inventionare. given below imparts ,by Any of the usual high boiling solvents may be used, but should be selected according to their a a Dry magnesia and glossy and relatively scratch-proof, so that a top coat of protective varnish is not necessary to ,metal surfaces to which they areapplied. This is one of the most important characteristics of tion have been described in some detail, it should whereby the resulting ink, when printed on metal,

, Another type of varnish base is given below: Exsivrrrn VI .-Yqrnish base Phenol-formaldehyde resin modified with a natural resin (A merol) 150 5 Raw tung oil 80 This mixture Was'heated to 560 F. in hou and then the following were added:

60 The mixture was then brought to 500 F. m

minutes and held for hour, 1. e., to'the point of gelation. Then was added:

When applied to tin plate and baked, these inks dry in approximately 3-5 minutesat a temperature of about 200--220 FE, depending on the type and proportion of solvent used. While the usual tin printing inks. require an ageing period of 7-14 days before they can, be cut or formed on the dies orother forming tools, the inks of my invention are hard enough to withstand the forming operations in only 24'hours. I

These inks dry to a very hard surface which is protect the ink from marring, although, of course, such a varnish may be applied if desired. My new inks exhibit excellent adhesion to the this type of ink, as it must withstand shaping and forming operations without chipping or-flaking off or loosening its hold on themetal base. 7

While the preferredembodimentsof my invenbe understood that the invention is not to be limited to the precise details described, but may be carried out in other ways.

I claim as my invention: 1. The method of preparing a printing ink which comprises heating a resin selected from the group consisting of aphenyl substituted phenol-formaldehyde-drying-oil modified resin,

anv alkyl substituted phenol-formaldehyde-dry- 0 'ing-oil-mod'ified resin, a phenol-formaldehyde natural resin condensation product; with drying oil to the point of incipient gelation, adding a solvent; then continuing the polymerization but preventing gelation which would otherwise occur, by further heating in the presence of said solvent forabout two andone-half to three hours, at a temperature of about 190 to 210 C., and thereafter cooling and grinding with a pigment,

will dry at a temperature of 200 to 220 F. in from three to five minutes.

2. The method of preparing a printing ink which comprises heating a resin selected from the group consisting of a phenyl substituted phe- 76 nol-formaldehyde-drying-oil-modified resin, an alkyl substituted phenol-formaldehyde-dryingoil-modified resin, a phenol-formaldehyde natural resin;condensatio'n. product; with drying oil to the point of incipient gelation, adding a solvent and a plasticizer; then continuing the polymerization but preventing gelation which would otherwise occur, by further heating in the presence of said solvent and of said plasticizer for about two and one half. to three hours, at a'temperature of about to 210 0., and thereafter cooling and grinding with a pigment, whereby the resulting ink, when printed on metal,will dry at a temperature of 200 to 220 F. in from three to five minutes. 1 T

-3. The method of preparing aprinting ink which comprises heating a resin selected from the group consisting of a phenyl. substituted phenolformaldehyde drying-oil-rnodified resin, an alkyl substituted phenol formaldehyde -'drying-oilmodified resin, a phenol-formaldehyde natural resin condensation product; with tung oilto the point of incipient gelation, adding a solvent; then continuing the polymerization but preventing gelation which would otherwise occur, by further heating in the presence of said solvent for about two and one half to .three hours; at a temperature of about 190to 210 0., and" thereafter cooling and grinding with a pigment, whereby theresulting ink, when printed on metal, will dry at a-tem perature of 200'to 220 F. in from three to five minutes 4. The method of preparing a printing ink which comprises heating a phenyl substituted phenol-formaldehyde-drying-oil-modified resin, with a'drying oil totthe point of incipient gelation, adding a solvent and a plasticizer, continu ingthe polymerization but preventing gelation which would otherwise occur, by further heating in the presence of the solvent'and the plasticizer, v

for about two and one half to three hours at a temperature of about 190 to 210C and thereafter cooling and grinding with a pigment,

wherebythe resulting ink, when printed on metal, will dry at a temperature of 200 to 220 Frin from three to five minutes. I, g 5. The method of preparing a printing ink which comprises heating a resin selected from the group consisting of a phenyl substituted phenol-formaldehyde-dryingmil-modified resin,

an alkyl substituted phenol-formaldehyde:drying-oil-modified resin, a phenol-formaldehyde natural resin, condensation product; with dryi g oil to the point of incipient gelation, addi ng benzyl alcohol; then continuing the-polymerization but preventing gelation which would otherwise occur, by further heating in the presence of said benzyl alcohol for abouttwo and one-half to three hours, at a temperature of about 190 to 210 C., and thereafter cooling and grinding' with a pigment; whereby the resulting ink; when printed on metal, will dry at a temperature of 200 to 220 F. in from three to five minutes."

6; The method of preparing a printing ink which comprises heating aresin selected from the group consistingof a phenyl substituted phenol-formaldehyde-drying-oil-modified resin, an alkyl substituted 'phenol formaldehyde-dryi ng-oil-modifled resin, a phenol-formaldehyde natural resin condensation product; with drying -oil to the point of incipient gelation, adding cyclohexanone; then continuing the polymerization but preventing gelation which' would otherwise occur, by iurtherheating in the presence of said cyclohexanone for about two and one-half to three hours, at a temperature of about 190 to 210 0., andthereafter cooling and grinding with a pigment, whereby .the resulting ink, when printed onmetal, will dry at a temperature of 200 to 220 F. in from three to flve minutes,

, adding benzyl alcohol and a plasticizer, continu- 7. The method of preparing a printingink which comprises heatin a resin selected from I the group consisting of a phenyl substituted phenol-formaldehyde-drying-oil-modified resin, an alkyl substituted phenol-formaldehyde-drying-oil-m-odified. resin, a phenol-formaldehyde natural resin condensation product; with drying oil to the point or incipient 'gelation, adding hexalin; then continuing the polymerization but preventing gelation which would otherwise occur, by further heating in the presence of said hexalin for about two and one-halt tothree hours, at a temperature of about 190] to 210 0.,

and thereafter cooling and grindingwith a pig-f ment, whereby the resulting ink, when printed on metal, will dry at a temperature of 200 to 220 F. infrom three .to five minutes.

8. The method of. preparing a printing ink which comprises heating, a phenyl substituted phenol-iormaldehyde-drying -oil-modifled resin,

with tung oil to the point of incipient gel'ation,

mg the polymerization but preventing gelation which would otherwise occur, by further heating .in the presence of the benzyl alcohol and the plasticizer, for about two and one-half to three jhoursat a temperature of about to 210 C..

and thereafter cooling and grinding with a pigmerit, whereby the resulting ink, when printed on metal, will dry in from three to five minutes.

'9. A quick drying printing ink for printing on metal made in accordance with the process of claim 1.

10. 'A quick drying printing ink for printing on metal made in accordance with the process of claim 2.

11. A quick drying printing ink for printing on metal made in accordance with the process of claim 3.

' on metal made in accordance with the process of claim 8.

JOSEPH G. CURADO; 

